Pumped loop driven vapor compression cooling system

ABSTRACT

A cooling system is provided that combines a two-phase refrigerant pumped loop cooling circuit and a vapor compression loop circuit in a complete electronics cooling package for use in high ambient temperature applications. Specific applications may include, but are not limited to, power electronics converter and inverter drives, and hybrid electric vehicles. In hybrid electric vehicle applications, the primary pumped two-phase refrigerant cooling system is used for providing high-temperature cooling to the inverter drive. The secondary vapor compression system is used to provide low-temperature cooling to the battery module (i.e. such as Li-ion cells) or passenger compartment cooling, thereby eliminating the need for a special cooling solution for the battery module which requires lower temperature cooling.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage Application of PCT Application No. PCT/US2010/036311 filed May 27, 2010 to which this application claims priority and benefit of U.S. Provisional Patent Application Ser. No. 61/182,237, file May 29, 2009, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates, in general, to a cooling system and method for cooling heat generating components, and in particular to a dual cooling system for providing cooling at two or more temperature levels and heat loads.

BACKGROUND

Electrical and electronic components (e.g. microprocessors, IGBTs, power semiconductors etc.) housed on a rack in a cabinet are most often cooled by air-cooled heat sinks with extended surfaces, directly attached to the surface to be cooled. A fan or blower moves air across the heat sink fins, removing the heat generated by the component. With increasing power densities, miniaturization of components, and shrinking of packaging, it is sometimes not possible to adequately cool electrical and electronic components with heat sinks and forced air flows. When this occurs, other methods must be employed to remove heat from the components.

SUMMARY

At least one embodiment of the invention provides a cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and a plurality of electronic heat sources thermally coupled to a plurality of cold plates; the second fluid circuit having a compressor, an evaporator, and an expansion valve; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.

At least one embodiment of the invention provides an electric hybrid vehicle cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and an inverter drive thermally coupled to a cold plate; the second fluid circuit having a compressor, an evaporator, and an expansion valve, wherein the second fluid circuit provides cooling to a battery module of the vehicle; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.

An electric hybrid vehicle cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and an inverter drive thermally coupled to a cold plate; the second fluid circuit having a compressor, an evaporator, and an expansion valve, wherein the second fluid circuit cools the passenger compartment of the vehicle; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this invention will now be described in further detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a pumped loop/vapor compression cooling system in accordance with an embodiment of the present invention wherein the components to be cooled in the pumped loop portion are shown in parallel;

FIG. 2 is a pressure enthalpy diagram for a refrigerant showing the first and second cooling circuits of the cooling system in accordance with an embodiment of the present invention; and

FIG. 3 is a schematic view of a pumped loop/vapor compression cooling system in accordance with an embodiment of the present invention wherein the components to be cooled in the pumped loop portion are shown in series.

DETAILED DESCRIPTION OF THE DRAWINGS

An embodiment of a pumped loop/vapor compression cooling system 10 is shown in schematic form in FIG. 1. The system 10 comprises a first closed loop fluid circuit 20 and a second closed loop fluid circuit 30. The first fluid circuit 20 provides the primary two-phase refrigerant cooling cycle and comprises a condenser 22 (having cool ambient air 50 flowing therethrough), a pump 24, and a plurality of electronic heat sources mounted on or thermally coupled to a plurality of cold plates 26, shown fluidly connected in parallel. The second fluid circuit 30 provides a secondary vapor compression refrigeration cycle and comprises a compressor 32, an evaporator 34 (having hot ambient air 52 flowing therethrough), and an expansion valve 36. A liquid to liquid heat exchanger 40 is positioned in the second fluid circuit and in the first fluid circuit in parallel with the plurality of cold plates 26. The heat exchanger 40 acts as an evaporator for the first circuit 20 and as a condenser for the second circuit 30.

The fluid circuits 20, 30 may include additional components as needed such as a liquid reservoir 28 positioned between the condenser 22 and pump 24. The evaporator 34 may exist as a cold plate evaporator of a cabinet chiller.

Operation of the system 10 is described herein with respect to FIG. 2 which shows a pressure enthalpy diagram for a R-134a refrigerant showing the relationship of pressure versus enthalpy for the two phase cooling cycle of the first circuit 20 and the vapor compression refrigeration cycle of the second circuit 30. The numbers on the diagram represent the locations of the fluid in the system as shown in FIG. 1, with positions 1-3 being located in the first fluid circuit 20 and positions 4-7 being located in the second fluid circuit 30. The dotted line represents the liquid to liquid heat transfer between the circuits 20, 30.

Referring to the two-phase cooling cycle of the first circuit 20, at position 1 the refrigerant fluid exists as a sub-cooled liquid prior to entry into either the plurality of cold plates 26 or the liquid to liquid heat exchanger 40. Heat is added to the fluid which partially evaporates while passing the plurality of cold plates 26 or the liquid to liquid heat exchanger 40 to the position designated at 2. The cool ambient air 52 cools the partially evaporated fluid to a liquid phase which travels to the liquid reservoir 28 until needed by the pump 24. The position 3 represent the slightly sub-cooled fluid entering the pump 24 which increases the fluid pressure, returning the sub-cooled fluid to the first position 1.

Referring to the vapor compression refrigeration cycle of the second circuit 30, at position 4 the refrigerant exists as a slightly superheated vapor that enters the compressor 32 increasing the pressure and enthalpy by compressing the superheated vapor shown at position 5 ready for entry into the liquid to liquid heat exchanger 40. The liquid to liquid heat exchanger 40 cools the superheated vapor to a sub-cooled liquid shown at position 6 exiting the liquid to liquid heat exchanger 40. The expansion valve 36 reduces the pressure of the sub-cooled liquid which partially vaporizes the fluid prior to entering the evaporator 34 as shown at position 7. The hot ambient air 50 entering the evaporator 34 causes the partially vaporized fluid to change to a superheated vapor exiting the evaporator 34 as shown again at position 4.

In another embodiment of the invention as shown in FIG. 3, the cooling system 10′ is the same as the cooling system of FIG. 1 except that the pumped loop or first fluid circuit 20′ comprises a plurality of electronic heat sources mounted on or thermally coupled to a plurality of cold plates 26, shown fluidly connected in series.

In use, the dual cooling system 10 provides a complete electronics cooling package for use in high ambient temperature applications. Specific applications may include, but are not limited to, power electronics converter and inverter drives, and hybrid electric vehicles. In power electronics converter and inverter drives, the primary pumped two-phase refrigerant cooling system is used for providing high-temperature cooling to IGBTs and other electronic components. The secondary vapor compression system is used to provide low-temperature cooling to the drive cabinet, thereby eliminating the need of an external air conditioner. In hybrid electric vehicles, the primary pumped two-phase refrigerant cooling system is used for providing high-temperature cooling to the inverter drive. The secondary vapor compression system is used to provide low-temperature cooling to the battery module (i.e. such as Li-ion cells) or passenger compartment cooling, thereby eliminating the need for a special cooling solution for the battery module which requires lower temperature cooling.

Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention. 

1. A cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and a plurality of electronic heat sources thermally coupled to a plurality of cold plates; the second fluid circuit having a compressor, an evaporator, and an expansion valve; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.
 2. The system of claim 1, wherein the first loop further comprises a liquid reservoir between the condenser and the pump.
 3. The system of claim 1, wherein the plurality of cold plates of the first fluid circuit are fluidly connected in parallel.
 4. The system of claim 1, wherein the plurality of cold plates of the first fluid circuit are fluidly connected in series.
 5. The system of claim 3, wherein the liquid to liquid heat exchanger is fluidly connected to the first circuit in parallel with the plurality of cold plates.
 6. The system of claim 4, wherein the liquid to liquid heat exchanger is fluidly connected to the first circuit in series with the plurality of cold plates.
 7. The system of claim 1, wherein a source of hot ambient air is directed through the evaporator of the second fluid circuit.
 8. The system of claim 7, wherein the source of hot ambient air is obtained from air surrounding the electronic heat sources.
 9. The system of claim 1, wherein a source of cool ambient air is directed through the condenser of the first fluid circuit.
 10. The system of claim 9, wherein the source of cool ambient air is obtained from a source of air outside the cooling system.
 11. An electric hybrid vehicle cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and an inverter drive thermally coupled to a cold plate; the second fluid circuit having a compressor, an evaporator, and an expansion valve, wherein the second fluid circuit provides cooling to a battery module of the vehicle; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.
 12. The system of claim 11, wherein the first loop further comprises a liquid reservoir between the condenser and the pump.
 13. The system of claim 11, wherein a source of hot ambient air is directed through the evaporator of the second fluid circuit.
 14. The system of claim 17, wherein the source of hot ambient air is obtained from air surrounding the battery module.
 15. An electric hybrid vehicle cooling system comprising: a first fluid circuit and a second fluid circuit; the first fluid circuit having a condenser, a pump, and an inverter drive thermally coupled to a cold plate; the second fluid circuit having a compressor, an evaporator, and an expansion valve, wherein the second fluid circuit cools the passenger compartment of the vehicle; and a liquid to liquid heat exchanger positioned in the first and second fluid circuits such that a second fluid flowing through the second fluid circuit is cooled by a first fluid flowing through the first fluid circuit.
 16. The system of claim 15, wherein the first loop further comprises a liquid reservoir between the condenser and the pump.
 17. The system of claim 11, wherein a source of hot ambient air is directed through the evaporator of the second fluid circuit. 